Wireless item location monitoring system and method

Abstract

A wireless electronic tracking system employs transmitters attached to moveable target items that send continuous analog radio frequency (RF) digitally-coded signals at prime number differentiated time intervals to a base receiver. The coded signals carry transmitter and base unit identifiers, low battery and attachment status information. The base unit periodically scans using an omnidirectional antenna to determine distance and azimuth for multiple active transmitters, alerting an operator to any status alerts, such as ‘out of range’ status determined by signal strength. The operator can switch to a higher gain, directional antenna to search for an errant target transmitter, or simply to check on the whereabouts of any given target item. Because the movable target items need only transmit, the transmitters can be physically diminutive and unobtrusive to the target wearer, making the system practical for tracking people (e.g. geriatric or juvenile, for assistance or to deter leaving group members behind), animals (e.g. pets, livestock) and even inventory (e.g. especially expensive items that shouldn't move from a given spot in a retail setting).

1. A monitoring system for movable targets comprising
 a plurality of target-borne transmitters, each transmitter having a case;
 attachment means for attaching the case to the target; 
 a radio-frequency signal generator housed within the case and adapted to generate and repeatedly to transmit a coded signal at a selected radio frequency and separated by a selected prime number time interval; 
 a transmitter antenna coupled to the signal generator; and 
 a battery within the case and coupled to signal generator; and 
 
 a base unit adapted to monitor the transmitters, the base unit having
 a housing having an interior and a face; 
 signal detection means within the housing for
 listening at the selected frequency and prime number time interval for each transmitter; and 
 receiving the coded signals from the transmitter signal generator transmitting at its selected prime number time interval; 
 
 a database within the housing and containing information about each target and the transmitter's selected prime number time interval; 
 processing means within the housing and adapted to
 detect coded signals from the signal detection means; 
 process the coded signals to update the database means with information about the transmitter attached to each target; and 
 sound an alarm for an out-of-range condition of any transmitter; 
 
 operator interface means for providing an operator with control of the processor means and information about each target; and 
 power means for providing power to the base unit. 
 
 
     
     
       2. The monitoring system according to  claim 1  wherein the attachment means further comprises
 disconnect loop means surrounding at least a portion of the target for detecting a disconnection of the transmitter from the target; and 
 the signal generator initiates an alarm status within the coded signal if the transmitter becomes disconnected from the target. 
 
     
     
       3. The monitoring system according to  claim 2  wherein the disconnect loop means comprises
 the transmitter antenna. 
 
     
     
       4. The monitoring system according to  claim 1  wherein the signal detection means comprises
 a radio-frequency receiver within the housing and coupled to the processing means; and 
 an antenna system having
 an omnidirectional antenna and a directional antenna; and 
 antenna selection means for selectively coupling the omnidirectional antenna and the directional antenna to the signal detection means. 
 
 
     
     
       5. The monitoring system according to  claim 4  wherein the antenna selection means comprises
 a three-way switch on the operator interface means and coupled between both of the antennas and the processing means. 
 
     
     
       6. The monitoring system according to  claim 1  wherein the operator interface means comprises
 an antenna selection switch; 
 an acknowledge button adapted to initiate a transmitter alarm acknowledgment routine; 
 an find button adapted to activate a transmitter search routine; and 
 a liquid crystal diode disposed on the face and adapted to display information from the processing means. 
 
     
     
       7. The monitoring system according to  claim 1  wherein the power means comprises
 a battery. 
 
     
     
       8. The monitoring system according to  claim 1  wherein the processing means comprises
 a microprocessor coupled to the signal detection means and the database and adapted to
 separate the coded signal into individual bytes; 
 analyze at least one of the coded signal bytes to identify each transmitter and to compare it to the information in the database; 
 analyze at least one of the coded signal bytes to identify the base unit to which the transmitter is signaling; 
 analyze a third byte to determine distance and direction of the transmitter from the base unit; and 
 detect and correct errors in the coded signal. 
 
 
     
     
       9. The monitoring system according to  claim 1  wherein the coded signal further comprises
 a digital word having
 a transmitter identifier byte; 
 at least one base unit identifier byte; 
 an error detection and correction byte; and 
 a signal strength byte. 
 
 
     
     
       10. The monitoring system according to  claim 9  wherein
 the signal strength byte is fixed at maximum value. 
 
     
     
       11. The monitoring system according to  claim 9  and further comprising
 a low battery condition code. 
 
     
     
       12. A remote target monitoring system comprising
 a transmitter for each target, the transmitter having
 a signal generator coupled to a transmitter antenna and adapted to generate a coded signal through the transmitter, the coded signal containing at least one digital word having
 a transmitter identifier byte; 
 at least one base unit identifier byte; 
 an error detection and correction byte; and 
 a signal strength byte; and 
 
 an attachment coupling the transmitter to the target; and 
 
 a base unit adapted to monitor a plurality of transmitters, the base unit having
 a coded signal detector adapted to detect each transmitter's coded signal using its transmitter identifier byte and its at least one base unit identifier byte; 
 a signal processor coupled to the detector and adapted to analyze the transmitter coded signals to;
 determine a status of each transmitter using its coded signal error detection and correction byte; 
 determine a direction and distance of each transmitter from the base unit by using its signal strength byte; 
 store status information about each transmitter into a database; 
 detect an out of range condition for any active transmitter from its signal strength byte;and 
 activate an alarm for any transmitter having an out of range condition; and 
 
 a user interface coupled to the signal processor and adapted to display information about each target and transmitter to an operator. 
 
 
     
     
       13. The monitoring system according to  claim 12  wherein the user interface further comprises
 an antenna selector coupled to the signal detector and adapted to selectively couple one of an omnidirectional antenna and a directional antenna to the signal processor; 
 a liquid crystal display coupled to the signal processor and adapted to selectively display numeric and signal strength data; 
 an alarm acknowledgment switch; and 
 a search activation switch. 
 
     
     
       14. The monitoring system according to  claim 12  wherein the signal detector further comprises
 a radio-frequency receiver within the housing and coupled to the signal processor; and 
 an antenna system having
 an omnidirectional antenna and a directional antenna; and 
 an antenna selector coupled to the signal detector and adapted to selectively couple one of the omnidirectional antenna and the directional antenna to the signal processor. 
 
 
     
     
       15. The monitoring system according to  claim 12  wherein
 the signal processor is programmed to
 separate the coded signal into individual bytes; 
 analyze the error detection and correction byte to assure that the coded signal may be analyzed; 
 analyze transmitter byte to identify the transmitter and associate the coded signal with information in the database about the target to which the transmitter is attached; 
 analyze the at least one base identifier byte to confirm that the transmitter is transmitting to the base unit; and 
 analyze the signal strength byte to determine distance and direction of the transmitter from the base unit. 
 
 
     
     
       16. An improved method of monitoring a plurality of movable items, the method comprising
 providing
 a plurality of transmitters, one each coupled to one of the movable items, the 
 transmitter having a case containing
 a signal generator coupled to an antenna; 
 a potentiometer coupled to the signal generator and adapted to control the strength of the signal; and 
 a battery powering the signal generator; and 
 
 a base unit adapted to monitor a plurality of transmitters, the base unit having
 signal detection means for detecting signals; 
 signal processing means coupled to the signal detection means for analyzing the signals to;
 determine an active status of each transmitter; 
 determine a direction and distance of each transmitter from the base unit; 
 store status information about each transmitter into a database; 
 detect an out of range condition for any active transmitter; 
 activate an alarm for any transmitter having an out of range condition; and 
 
 
 user interface means for providing a user with information about the items and transmitters; then 
 
 coupling a transmitter to each movable item; then 
 activating the transmitter to begin transmitting coded signals; then 
 setting the signal processing means to active status for each transmitter coupled to a movable item; then 
 monitoring each transmitter in turn to observe if it has an out of range condition; then 
 searching for any transmitter having an out of range condition with the base unit. 
 
     
     
       17. The improved method of  claim 16  wherein the signal detection means comprises
 a radio-frequency receiver coupled to the signal processing means; 
 an antenna system coupled to the receiver and having
 an omnidirectional antenna; 
 a directional antenna; and 
 antenna selection means for alternately coupling the omnidirectional antenna and the directional antenna to the receiver. 
 
 
     
     
       18. The improved method of  claim 17  wherein the searching step further comprises
 switching antenna system to couple the directional antenna to the receiver; then 
 inspecting the user interface means to confirm that the out-of-range transmitter can be detected; then 
 rotating the base unit in a horizontal plane while monitoring the user interface means to determine the direction of greatest signal strength for the out-of-range transmitter; then 
 comparing the signal strength to a maximum signal strength to determine distance to the out of range transmitter; then 
 proceeding in the direction of greatest signal strength to approach the out-of-range transmitter. 
 
     
     
       19. The improved method of  claim 16  wherein the activating step further comprises
 adjusting the potentiometer to define a radial distance from the base unit that the movable item will be able to move without triggering an alarm; and 
 interrogating a prime-number generator to select a prime number interval at which to transmit the coded signals at the selected radio frequency. 
 
     
     
       20. A monitoring system for movable targets comprising
 a plurality of target-borne transmitters, each transmitter having
 a case; 
 attachment means for attaching the case to the target; 
 signal generating means within the case for generating a coded signal; 
 a transmitter antenna coupled to the signal generating means; and 
 a battery within the case and coupled to signal generating means; and 
 
 a base unit adapted to monitor the transmitters, the base unit having
 a housing having an interior and a face bearing an operator interface; 
 power means for providing power to the base unit; 
 signal detection means within the housing for receiving the coded signals; 
 a database containing information about each transmitter; and 
 a microprocessor within the housing and coupled to the signal detection means and the database, the microprocessor being adapted to
 detect coded signals from the signal detection means; 
 detect and correct errors in the coded signal; 
 analyze coded signal to identify each transmitter; 
 compare the transmitter to the information in the database; 
 identify the base unit to which the transmitter is signaling; 
 determine distance and direction of the transmitter from the base unit, update 
 the database means with information about the transmitter; and 
 sound an alarm for an out-of-range condition of any transmitter. 
 
 
 
     
     
       21. A monitoring system for movable targets comprising
 a plurality of target-borne transmitters, each transmitter having
 a case; 
 attachment means for attaching the case to the target; 
 signal generating means within the case for generating a coded signal having
 a transmitter identifier; 
 at least one base unit identifier; 
 error detection and correction means; and 
 a signal strength identifier; 
 
 a transmitter antenna coupled to the signal generating means; and 
 a battery within the case and coupled to signal generating means; and 
 
 a base unit adapted to monitor the transmitters, the base unit having
 a housing having an interior and a face; 
 signal detection means within the housing for receiving the coded signals; 
 database means within the housing and containing information about each target; 
 processing means within the housing and adapted to
 detect coded signals from the signal detection means; 
 process the coded signals to update the database means with information about the transmitter attached to each target; and 
 sound an alarm for an out-of-range condition of any transmitter; 
 
 operator interface means for providing an operator with control of the processor means and information about each target; and 
 power means for providing power to the base unit. 
 
 
     
     
       22. A remote target monitoring system comprising
 a transmitter for each target, the transmitter having
 a signal generator coupled to a transmitter antenna and adapted to generate a coded signal containing a digital word having a transmitter identifier byte, at least one base unit identifier byte, an error detection and correction byte, and a signal strength byte; 
 a case containing the signal generator; and 
 a battery powering the signal generator; 
 an attachment coupling the transmitter to the target; and 
 
 a base unit adapted to monitor a plurality of transmitters, the base unit having
 a database containing information about each transmitter; 
 a user interface adapted to display information about each target and transmitter; 
 a coded signal detector; 
 a signal processor coupled to the coded signal detector and adapted to analyze each coded signal from the plurality of transmitters to
 separate the coded signal into individual bytes; 
 analyze the error detection and correction byte to assure that the coded signal may be analyzed; 
 analyze the transmitter identifier byte to identify the transmitter and associate its coded signal with information in the database about the target to which the transmitter is attached; 
 analyze the at least one base identifier byte to confirm that the transmitter is transmitting to the base unit; 
 analyze the signal strength byte to determine distance and direction of the transmitter from the base unit 
 store status information about each transmitter into the database; 
 detect any out of range condition for the transmitter; and 
 activate an alarm for any transmitter having an out of range condition.